Free piston well pump



Sept. 11, 1956 D. G. KNOX 2,762,309

FREE PISTON WELL PUMP Original Filed July 25, 1949 4 Sheets-Sheet 1 BY 5M Sept. 1'1, 1956 D. G. KNOX FREE PISTON WELL PUMP Original Filed July 25, 1949 I'ZI ' I'Z'Z 4 Shets-Sheet 2 Sept. 11, 1956 D. G. KNOX FREE PISTON WELL PUMP 4 Sheets-Sheet 3 Original Filed July 25, 1949 & Ill

DOA/9L0 '83 591/552 0 94x prroeueys' p 11, 1956 D. G. KNOX 2,762,309

FREE PISTON WELL PUMP Sheet-Sheet 4 Original Filed July 25, 1949 ;5 I BY arroeu vs Uited States Patent FREE PISTUN WELL PUMP Donald G. Knox, Rolling Hills, Califi, assignor to The National Supply Company, Pittsburgh, Pa., a corporation of Pennsylvania Original application July 25, 1949, Serial No. 106,579. Divided and this application September 18, 1953, Serial No. 381,015

11 Claims. (Cl. 103-52) This invention relates to free piston pumping apparatus and is particularly directed to improvements over devices of the type shown in my copending application filed August 8, 1947, hearing Serial No. 767,401, now Patent No. 2,661,024, and the copending applications of Knox et a1. filed November 1, 1945, Serial No. 626,052, now Patent No. 2,508,174 and filed March 28, 1949, Serial No. 83,850, now Patent No. 2,642,002. This application is a division of my copending application, Serial No. 106,579, filed July 25, 1949, now Patent No. 2,699,121, issued lanuary 11, 1955.

An important object of this invention is to provide an improved form of device for opening the plunger valve at the top of the well in discharge position, which device may be used successfully on wells having widely varying rates of production and widely varying gas pressure for operating the plunger.

Another important object of this invention is to provide positively operated means for closing the main valve in the eduction pipe leading from the well head when the plunger reaches the upper end of its stroke.

Another object is to provide a device of this type having a time lag mechanism, the action of whichis initiated by positive contact with the plunger at the top of the well and which acts to effect a positive closing of the main valve in the eduction pipe after a short interval of time.

Another obiect is to provide a device of this type in which means are provided for throttling the main valve in the eduction pip-e leading from the well head in the event that the pressure of the well fluid brought to the surface by the plunger should exceed a predetermined safe value in order to lessen the shock of stopping the plunger at the upper end of its travel and also to protect apparatus such as traps, etc. connected to the eduction pipe downstream from the main valve.

Other objects and advantages will appear more fully hereinafter.

In the drawings,

Figure 1 is a side elevation partly in phantom lines snowing connections at a well head of the type incorporated in connection with my invention and showing preferred embodiments of my invention in outline form.

Figure 2 is a side elevation partly in section showing one form of valved plunger which may be used in connection with this invention.

Figure 3 is a sectional elevation partly broken away showing a preferred form of apparatus :for positively opening the plunger valve at the upper end of the travel of the plunger.

Figure 4 is a sectional elevation which constitutes continuation or" the lower end of Figure 3. Figure 4 also shows a preferred form of plunger contacting element having the function of initiating action in a control system for closing the main valve in the eduction line leading from the well head.

Figure 5 is an elevation view partly in section shown on an enlarged scale taken in the direction 55 as shown in Figure 4.

Figure 6 is a sectional plan view partly broken away showing constructional details of certain of the parts shown in Figures 4 and 5. V

Figure 7 is asectionalelevation partly broken away taken substantially on the lines 77 as shown in Figure 6'.

Figure 8 is a side elevation partly in section showing a ortion of the apparatus shown in Figure 6.

Figure 9 is an elevation partly in section showing con struction of a preferred form of control valve for th eduction pipe leading from the well. 7

Referring to the drawingsf p The well head generally designated 10 is shown in phantom lines and may include a shut-oil gate'valve 11 at the upper end thereof. Tubing 12 extends downward into the well and is connected at its upper end to the master gate valve 11 which in turn is connected to the stack nipple 13. When the valved plunger moves u wardly through the tubing'lZ through the master gate valve 11 and into the stack nipple 13 the valve in the plunger is positively opened by mechanical means so that the plunger drops back down through the tubing 12 to bring up another load of well fluid. Each load of well fluid brought upthrough the tubing 12 by the valved plunger passes into the stack nipple and out through lateral pipes 14 and 15. The pipe 15 is connected to the bumper housing 16 at the upper end of the stack nipple '13. The Well fluid then passes through shut-off valves 17 and 18 through the adjustable bean 19 and through the motor valve 20 to the gathering line 21. When the plunger enters the stack nipple 13 it strikes a trip cam in the actuator assembly 22, thereby initiating a sequence of actions which closes the line 23 and bleeds the line 24 to atmosphere.

There is a time delay while the line 24 is bled to atmospheric pressure. Bleeding of the line 24- causes the control instrument generally designated 25 to bleed to atmosphere the line 26, and the pressure supply pipe 27 is also bled down to atmosphere. The consequent reduction in pressure within the motor 28 of the motor operated flow control valve 20 causes the spring 29 to move the valve stem 30 upwardly to close the valve. Closing of the main control valve 20 shuts in the tubing 12 against pressure loss. Gas pressure admitted into the casing through the fitting 31, valve 32 and well head 10 then serves to build up pressure in the casing so that the plunger may again bring up a load of well fluid through the tubing 12. As the casing pressure rises the pressure is communicated through line 33 to the terminal 34 on the control instrument 25. The action of the control instrument is to pressurize the terminal 35 so that pressure passes through the line 27 to cause the motor 28 to open the valve 20 against the action of the spring 29. Since the valve 20 is open when the plunger and its load of well fluid approaches the well head 10, the well fluid passes through the valve 20 and out through the gathering line 21. Pilot gas under relatively low pressure is supplied to the control instrument 25 through the supply line 36. This pressure may be derived from any suitable or desirable source. As shown in the drawings, it may be obtained through line 37, check valve 38, regulator 39 and filter 40.

The type of plunger shown in Figure 2 represents one design which may be successfully operated in connection with my invention, but it is to be understood that other forms of valved plungers may also be used with good results. For example, the forms of plungers shown in my copending applications identified above may be used if desired.

Proceeding to a more detailed description of a preferred embodiment of my invention, the bumper housing 16 is connected by threads to the upper end of the stack mpple13 and is centrally bored to provide an internal chamber 41 for a bumper spring 42. The upper end of the bumper spring 42 engages the underside of the bumper cap 43 which is threaded into the upper end of the bumper housing 16. The lower end of-the bumper spring rests on a flanged collar 44 which in turn rests on an abutment 45 provided in the bumper housing 16. The flanged collar is fixed to a central vertical spear tube 46 which extends downward from the bumper housing 16 centrally into the stack nipple 13. When the valved plunger assembly generally designated 9 moves upward into the stack nipple 13 at the upper end of its stroke, the plunger telescopes over the relatively stationary spear tube 46 so that the latter is received'within the central bore 47 in the plunger 9. When the plunger approaches the upper limit of its movement the lower end 48 of the speartube strikes the valve 49in the plunger 9 and moves it down into the range of action of the magnet 49a. The valve 49 is thus positively opened by a relative motion between the plunger 9 and spear tube 46. As soon as the valve 49 is opened the plunger drops downward by gravity through the tubing and into the lower portion of the well. The valve 49 remains open until it is closed by a suitable bumper in the lower portion of the well, as will be readily understood by those skilled in the art.

The proportions of the spear tube 46 and plunger 9 are such that the upper end 50 of the plunger strikes the flanged collar 44 before the valve 49 reaches fully open position. The shock of stopping the plunger in its forward travel is therefore taken directly on the flanged collar 44 and imparted to the bumper spring 42. The collar may be ported as shown at 51 and the spear tube may be provided with a central opening 52 in order to provide flow passage area so that a portion of the well .fluid brought up through the tubing by the plunger 9 may pass into the chamber 41 and out through the pipe 15 and valve 17.

The mechanism just described for positively opening the valve in the plunger represents a very valuable feature for it insures that the plunger will drop back into the well promptly after it delivers a load of well fluid. In prior forms of free piston pumping devices a reduction in pressure below the valved plunger was relied upon to permit the valve to open by gravity. Such a construction gives good results in many cases, but in some installations A packing gland 62 encircles the pivot shaft 57 where it emerges from the bearing 60, and this gland is threaded to the bearing 60 in order to compress packing material 63 to prevent leakage of gas or well fluid be tween the pivot shaft 57 and the bearing 60. From this description it will be understood that the cam 53 is adapted to turn the horizontal pivot shaft 57 when the upper end 50 of the plunger 9 strikes the projecting cam 53. A limit stop 64 is provided on the lower end of the cam 53 and is adapted to engage an abutment 65 formed on the stack nipple 13 to limit movement of the cam '53 into the bore 55 of the stack nipple.

A boss 66 is fixed to the outer projecting end of the horizontal pivot shaft 57 by means of a set screw 67. This boss is connected as by welding or brazing to a trigger arm 68 which extends radially from the pivot shaft 57. As shown in Figure 7, this trigger arm 68 is engaged by one end of a coil spring 69 which acts to hold where the volume of gas in the well is low the plunger may approach the well head slowly and float in a position just below the discharge nozzle, and thus fail to return promptly and bring up another load of fluid. The positive opening feature of the present invention avoids this difficulty, and the device is of universal application in that it operates successfully on wells having either a large or small volume of gas available for raising the plunger. Furthermore, sticking of the plunger valve 49 in closed position is positively overcome by the provision of this mechanical opener.

Positively actuated means are provided for closing the main valve 20 when the plunger arrives at the well head. As shown in the drawings a tripping cam 53 is mounted in a vertical slot 54 provided in the stack nipple 13. This cam 53 has a portion thereof that projects into the cylindrical bore 55 of the stack nipple. The cam 53 is provided with a transverse boss 56 mounted outside the stack nipple 13. This boss is fixed to a pivot shaft 57 by means of set screws 58, and the pivot shaft is supported for turning movement in axially aligned bearings 59 and 60. The bearings project through the wall of the pipe 14 which projects laterally from the stack nipple 13. Lateral ports 61 are drilled into the stack nipple 13 in alignment with the interior of the lateral pipe 14 so that a part of the well fluid brought up by the plunger 9 may pass through these ports and out through the lateral pipe 14.

the limit stop 64 on the lower end of the cam in contact with the abutment 65. The tension in the spring may be adjusted by means of the rod 70 and thumb screw 71. A trigger arm spring 72 is fixed to the trigger arm 68 by means of suitable screw connections 73. The outer end of this trigger arm spring 72 overlies the projecting end 74 of a valve 75. This valve 75 is provided with a conical sealing surface 76 which is adapted to engage a cooperating seat 77 provided within the valve body 78. The valve 75 is slidably mounted within the bore 79 in the valve body 78. A cap 80 is provided with a central aperture through which the end 74 of the valve 75 projects. The cap 80 may be threaded to the valve body 78. It will be observed that the spring 69 which maintains the striker cam 53 in projecting position also moves the trigger arm spring 72 in a direction to hold the valve in closed position, that is, with the surfaces 76 and 77 in engagement.

The valve body 78 may be supported in any convenient manner, and as shown in the drawings it is carried on a bracket 81 fixed as by welding to a C-shaped supporting bracket 82. This bracket may be mounted on the lateral pipe 14 by means of threaded fastenings 83 which connect to lateral ears 84 welded to the pipe 14.

A terminal fitting 85 connects with the line 24 and connects with the bore 88 in the valve body 78. This terminal fitting establishes communication between the line 24 and the chamber 86 at one end of the bore 88. The plunger 87 slides loosely within the bore 88 in the valve body. A compression spring 89 in the lower end of the bore rests on the threaded plug 90 and exerts a force tending to move the sliding plunger 87 toward the valve 75. The space 91 between the plug 90 and the plunger 87 receives the spring 89, and this space is in communication with the terminal fitting 92 and its connecting pipe 93. The spring 89 acts on the plunger 87 to move it into contact with the small lower projection 94 on the valve 75. The plunger is prevented from separating the sealing surfaces 76 and 77 because the trigger arm spring 72 normally holds the surfaces in engagement. During the time that the valve 75 is closed, gas under pressure supplied through line 24 passes inwardly through the fitting 85 into the chamber 86 and around the plunger 87 into the space 91 and out through the terminal fitting 92 and connecting pipe 93 to the T-fitting 114 and line 23. The pilot gas thus circulates between the pilot valve generally designated 131 and the control instrument 25 so long as the cam 53 is not operated.

When the cam 53 is actuated by the plunger assembly 9, however, the pivot shaft 57 is turned in a direction to lift the trigger arm spring 72 away from the projecting end 74 of the valve 75. The spring 89 then raises the valve 75 away from the seat 77. The upper conical end of the plunger 87 engages the conical seat 87a in the body 78 closing the line 93. Accordingly, the pressure in the line 24 is bled down through the terminal fitting 85, chamber 86, bore 79 and through the aperture 9.5 in the cap 80. The valve 75 may be grooved to facilitate.

venting of gas pressure through the bore 79 and out through aperture 95.

If the plunger 9 should strike the cam 53 and then immediately drop back into the well, the trigger arm spring 72 would re-engage the end 74 of the valve 75 and return it to closed position before the line 24 could be bled down to atmospheric pressure. Accordingly, means are provided for latching the trigger arm 68 and trigger arm spring 72 in raised position so that the valve 75' will remain open for a desired time interval. As shown in the drawings, this means includes a latch bar 96 which is pivoted at 97 on a post 98. The post 98 is adjustably secured to the C-shap'ed supporting bracket 82 by means of clamping nuts 99. A compression spring 100 contacts the C-shaped supporting bracket at one end and at the other end rests against the button 101 mounted on the latch bar 96. The spring 100 normally acts to pivot the latch bar 96 in a direction so that the swinging end 102 of the latch bar may engage under the lower edge 103 of the trigger bar 68; The force exerted by the spring 100, however, normally is opposed by a force applied to the latch bar 96 by means of the pin 104 carried at the end of the slotted plunger 105. The latch bar 96 extends through the slot 106 in the projecting end of the plunger 105.

As shown in Figure 6, the plunger 105 extendsthrough an opening 107 in the supporting bracket 82 and is encircled by an annular metallic bellows 108. The plunger is provided with a head 109 at one end which is sealed with respect to the end 110 of the bellows 108.

The bellows is enclosed within a shell 111 which forms.

av pressure chamber 112. The shell is sealed at one end by means of plate 113 and at the other end connects.

to a T-fitting 114. The T-fitting 114 also connects to the line 23 and to the branch pipe 93. The bellows assembly including the bellows 103 and shell 111 may be secured to the supporting bracket 82 by any convenient means such as, for example, by means of screw fastenings 115. A guard element 116 may be attachedto the C-shaped supporting bracket 82 by means of screw fastenings 117. This guard element partially encloses the bellows device. and its pressure connection fittings and thus serves to protect them from possible injury.

A compression spring 118 is positioned within the bellows and encircles a portion of the plunger 105. The action of the spring is. to extend the bellows. Pressure suppliedthrough the line 23 and T-fitting 114 enters the pressure chamber 112 and. acts to compressthe bellows in opposition to the spring 118.. A central tube. 119 within the bellows 108 acts as a limit stop to limit movement of the plunger 105 in a direction shortening the bellows 108.

The pressure in line 23 is sufficiently high so that the bellows contracts for its full working stroke and the end 1100f the bellows rests againstthe tubular stop 119. In this position the plunger 105 projects-inward so that the swinging end 102 of the latch bar 96 rests against the trigger bar 108. When the pivot shaft 57 is turned to lift the trigger bar 68 and trigger arm spring 72, the spring 100 moves the latch bar 96 so that the swinging end 102 is positioned under the lower edge 103 of the trigger bar 108. Lifting of the trigger arm spring 72 acts to bleed the line 23 as described above, and as the pressure in this line is reduced to atmospheric pressure the resilience of the bellows 108 causes it to lengthen, and this lengthening action is supplemented by the action of the spring 118. Accordingly, the plunger 105 is retracted to bring the pin 104 on the plunger 105 against the latch bar 96. When the pressure in the chamber 112 reaches atmospheric pressure the spring eiiect of the bellows corrugations supplemented by the force of the spring 118 is sufficient to pull the pivoted latch bar 96 back to the position shown in Figure 8. The spring 69 then swings the trigger bar 68 and trigger arm spring 72 back to the initial position,

6 thereby closing the valve and allowing pressure again to build up in the line 24 and to pass through the valve body 78 connecting pipe 93 and into the return line 23.

Whenever the pressure in the line 24 is. bled to atmosphere by the valve 75 as described above, the control instrument 25 acts to bleed the pressure at the terminal fitting 35 so that the line 27 is also bled to atmosphere. The control instrument 25 is of a type well known in the art used for providing atime record of pressure fluctuations. This instrument 25 acts as a supplementary pilot valve to supply pilot gas to the terminal 35 so long as pressure is maintained in line 24, and to bleed the terminal 35 when the pressure in line 24 is bled to atmosphere. As shown in Figure 9, reduction in pressure in the feed line 27' lowers the pressure in the space 120 above the'diaphragm 121. The spring 29 then raises the valve stem 30 to close the double-seated balanced valve assembly 122.

It is desirable to provide means for throttling the well fluid discharged from the well head inthe event that the pressure of the well fluid should exceed a safe value for the traps or other devices (not shown) connected with the gathering line 21. Also, throttle of the discharge line has the elfect of slowing down the plunger 9 to avoid damage upon impact with the bumper 44 in the well head. Thus, if a slug of well fluid under high pressure should be brought to the surface by the plunger 9, the control valve 20 will partially close to throttle the flow of well fluid therethrough, thereby reducing the pressure so that no damage will be done to equipment connected with the line 21. As shown in the drawings, the means for accomplishing this throttling eitect includes the branch line 123 connected at 124 to the flow line downstream from the control valve 20. This line 123 communicates with a space above a secondary diaphragm 125 positioned between the mating halves of a body 126. The diaphragm 125 is connected to stem 127, which stem operates a three-way valve 128. Thus, when excessive pressure is present downstream from the control valve 20, this pressure is communicated through line 23 to the diaphragm 125, thereby moving the stem downward to cause the gas pressure in line 27 to be vented through vent port 129. The relaxation of pressure in the space 120 above the diaphragm 121 then allows the spring 29 to move the double-seated valve assembly 122 toward a throttling positon. When the pressure downstream from the main valve 20 falls to a level which can be accommodated by the equipment connected at line 21, the reduction in pressure is communicated to the diaphragm 125 by the line 123 so that spring,

raises the stem 127 and again connects the space 120 above the diaphragm 12-1 directly with the line 27.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I claim:

1. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: a control valve operatively connected to the eduction tube to control flow therefrom, a movable element positioned adjacent the upper end of the eduction tube and adapted to be mechanically actuated by physical contact with said plunger when the plunger is near the upper end of its travel, and means for closing the control valve upon actuation of said movable element.

2. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: a control valve operatively connected to the eduction tube to corn trol flow therefrom, a movable element'positioned adjacent the upper end of the eduction tube and adapted to be mechanically actuated *by said plunger when the plunger is near the upper end of its travel, and pneumatically operated means including a pilot valve for closing the control valve upon actuation of said movable element.

3. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of can eduction tube in a well, the combination of: a control valve operatively connected to the eduction tube to control flow therefrom, a movable element positioned adjacent the upper end of the eduction tube and adapted to be mechanically actuated by said plunger when the plunger is near the upper end of its travel, and pneumatically operated means including a pilot valve and time delay means for closing the control valve upon actuation of said movable element.

4. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: a pressure operated control valve operatively connected to the eduction tube to control flow therefrom, a movable element positioned adjacent the upper end of the eduction tube and adapted to be mechanically actuated by physical contact with said plunger when the plunger is near the upper end of its travel, and pneumatically operated means for closing the pressure operated control valve upon actuation of said movable element.

5. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: a pressure operated control valve operatively connected to the eduction tube to control flow therefrom, a movable element positioned adjacent the upper end of the eduction tube and adapted to be mechanically actuated by said plunger when the plunger is near the upper end of its travel, and pneumatically operated means including time delay means for closing the control valve upon actuation of said movable element.

6. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: a pressure operated control valve operatively connected to the eduction tube to control flow therefrom, a movable element positioned adjacent the upper end of the eduction tube and adapted to be mechanically actuated by said plunger when the plunger is near the upper end of its travel, pneumatically operated means including a pilot valve for closing the control valve upon actuation of said movable element, and supplementary throttling means responsive to pressure of fluid passing through the control valve adapted to move the valve toward closed position.

7. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: a movable element having a portion thereof positioned in the path of movement of the plunger adjacent the upper end of the eduction tube, whereby said element may be mechanically actuated by said plunger when the plunger approaches the upper end of its travel, and means actuated by said movable element for controlling fiow from the eduction tube.

8. For use with a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the sub-combination comprising: a movable trigger element adapted to be positioned adjacent the upper end of the eduction tube, the trigger element having a portion thereof adapted to be mechanically actuated by said plunger when the plunger approaches the upper end of its travel, and means actuated by the movable trigger element for controlling flow from the eduction tube.

9. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: an outlet conduit leading from the eduction tube, a valve in said conduit controlling flow therethrough, a member forming a part of the eduction tube, a shaft mounted to turn relative to said member, a trigger element mounted on said shaft and having a portion extending into the path of travel of said plunger whereby the plunger may actuate said trigger element and turn the shaft, and pneumatically operated means for closing the valve in response to turning movement of said shaft.

10. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: an outlet conduit leading from the eduction tube, a valve in said conduit controlling flow therethrough, a member forming a part of the eduction tube, a shaft mounted to turn relative to said member, a trigger element mounted on said shaft and having a portion extending into the path of travel of said plunger whereby the plunger may actuate said trigger element and turn the shaft, an arm fixed to the shaft exteriorly of the said member, and pneumatically operated means for closing the valve in response to movement of said arm.

11. In a device having a valved plunger adapted to travel freely under pressure substantially the full length of an eduction tube in a well, the combination of: an outlet conduit leading from the eduction tube, a control valve in said conduit to control flow from said eduction tube, a member forming a part of said eduction tube, a shaft mounted to turn relative to said member, a movable trigger element fixed to the shaft and having a portion extending within said member for mechanical actuation by said plunger when the plunger approaches the upper limit of its travel, an arm fixed to the shaft exteriorly of said member, bias means acting to close the control valve, means including a pressurized control pipe for maintaining the control valve in open position in opposition to said bias means, and means whereby movement of said arm acts to vent the control pipe to atmosphere when the plunger actuates said trigger element, and thereby permit the bias means to close the control valve.

References Cited in the file of this patent UNITED STATES PATENTS 

